Clinical trials using antibodies that block the ligation of PD-1 (nivolumab, pembrolizumab) or CTLA-4 (ipilimumab), with their ligands, revealed them to be efficient in more than 15 cancer types, including metastatic melanoma, bladder carcinoma, non-small cell lung cancer, and breast and renal cell carcinoma [9–12]. The gene discussed is CTLA4; the disease is cancer.